Bump org.openjfx.version from 15 to 21

Bumps `org.openjfx.version` from 15 to 21.

Updates `org.openjfx:javafx-controls` from 15 to 21

Updates `org.openjfx:javafx-fxml` from 15 to 21

---
updated-dependencies:
- dependency-name: org.openjfx:javafx-controls
  dependency-type: direct:production
  update-type: version-update:semver-major
- dependency-name: org.openjfx:javafx-fxml
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

tool-parent/pom.xml

@@ -39,7 +39,7 @@
     </description>
 
     <properties>
-        <org.openjfx.version>15</org.openjfx.version>
+        <org.openjfx.version>21</org.openjfx.version>
     </properties>
 
     <modules>